From WO 2006/007086 A1 there is known a torque transmitting mechanism with a pump, a pressure store and a plurality of hydraulically actuatable couplings. The pressure store is filled by a pump. The couplings can be loaded with hydraulic pressure from the pressure store by operating the respective valves.
From WO 2006/128637 A1 there is known a drive unit with two friction couplings with a hydraulic actuator. According to one embodiment it is proposed that the two friction couplings are connected to one another via a short-circuit line with a safety valve. If the pressure in the first coupling drops, the hydraulic fluid can flow to the second coupling, with the first coupling being opened and the second coupling being closed.
From DE 2007 063 360 there is known a hydraulic assembly for one or several force-actuated setting units. The hydraulic assembly comprises a pump which is driven by a driveshaft of the motor vehicle and which generates a hydraulic pressure for actuating a piston-cylinder unit. The piston-cylinder unit serves to actuate a friction coupling by means of which it is possible to connect a secondary driving axle in the driveline of the motor vehicle. The hydraulic assembly can comprise a pressure accumulator which can be loaded by the pump and which can generate a relatively large volume flow for loading the piston-cylinder unit.
From DE 10 2008 037 886 there is known a drive assembly for a multi-axle driven motor vehicle. The drive assembly comprises a transfer case which distributes a torque introduced by an engine/motor to a first driving axle and to a second driving axle; it also comprises a propeller shaft which is arranged in the torque flow between the transfer case and the second driving axle. There is provided a first coupling at the first end of the propeller shaft and a second coupling at the second end of the propeller shaft. In the closed condition of the two couplings, torque is transmitted to the optionally connectable second driving axle. In the open condition of the two couplings, the propeller shaft with all the rotating components is disconnected from the engine and from the second driving axle, so that the propeller shaft is stationary.
DE 10 2004 033 439 B4 proposes a driveline for a motor vehicle with a friction coupling for transmitting torque and with an actuating assembly for actuating the friction coupling. The actuating assembly comprises a first pump which is suitable for quickly closing the friction coupling with a small amount of force, and a second pump which is designed for actuating the friction coupling with a large amount of force and a short stroke. The two pumps comprise different hydraulic ratios.